1. Field of the Invention
The present invention relates to a trigger switch, and more particularly, to a trigger switch having a trigger structure equipped with a stopper being improved strength.
2. Prior Art
As shown in FIG. 5A, a conventional electric power tool is composed of a body portion 111 and a handle portion 112 connected to the body portion 111. An electric motor for producing rotating power and a deceleration mechanism for decelerating the rotating power are accommodated in the body portion 111. The tool is rotationally driven according to the degree to which the trigger is pulled. A tool such as a grinder or metal saw is mounted to the front end of the body portion.
A trigger switch 113 having the trigger that is designed to be pulled directly by hand fingers is accommodated in the handle portion 112. As shown in FIGS. 5 and 6, the trigger switch 113 includes a control portion 114 and a switch body 115. The control portion 114 has a trigger capable of being manipulated by gripping power of a hand. The switch body 115 incorporates a switch that is turned on and off according to the degree to which the trigger is pulled.
The control portion 114 includes the trigger 116 directly touched by hand fingers and a return spring 117 accommodated inside the trigger 116. The spring 117 acts to return the pulled trigger to its original state.
The trigger 116 is bifurcated and has a touch portion 118, a first wall surface 119, and a second wall surface 121. The touch portion 118 has a bifurcated, curved back portion and is directly touched by fingers. The first and second wall surfaces 119 and 121 are parallel and opposite to the bifurcated portions. The first and second wall surfaces 119 and 121 are provided with pivotal holes 124 near the touch portion 118. A trigger support portion 122 extends from the switch body 115. A pivotal shaft 123 is mounted at the front end of the trigger support portion 122 and engaged in the pivotal holes 124.
A switch transfer portion 125 for turning on and off the contacts of the switch accommodated in the switch body is provided with a rotary bearing portion 126 at the front end thereof. An axial hole 127 is formed at the rotary bearing portion 126, and a rotary axial hole 128 is formed at the end opposite to the pivotal holes 124 to permit a fixture element 145 to be inserted and engaged.
A stopper portion 129 is mounted between the pivotal holes 124 and the rotary axial hole 128 to prevent fingers from being pulled in if the fingers touch the touch portion 118 near the rotary axial hole 128.
The stopper portion 129 has a guide slot 133 formed along the diameter of rotation, a metal plate 130 mounted inside the first wall surface 119, a stopper shaft 131 made of a guide rod 138, and a stopper button 143 mounted to an end of the stopper shaft 131 via a spring 144. The guide slot 133 acts to guide the stopper shaft 131 when the trigger 116 is pulled into the first wall surface 119 and rotated. The metal plate 130 has a stopper hole 132 that is slightly smaller than the guide slot 133. The stopper hole 132 extends in the same direction as the guide slot 133 and acts also as a stopper. A stopper member 136 having a cylindrical end portion having an enlarged diameter is mounted in the guide slot 133. The guide rod 138 is adjacent to the stopper member 136 but has a reduced diameter. The guide rod 138 is so long that it reaches the other second wall surface 121.
The metal plate 130 is mounted with the fixture element 145 engaged in the rotary axial hole 128 and with the pivotal shaft 123 engaged in the pivotal holes 124. The metal plate 130 has a stopper hole 132a narrower than the stopper hole 132 and a guide slot 133a narrower than the guide slot 133.
In the trigger switch having the structure as described so far, if fingers are brought into contact with the touch portion 118 and the touch portion is pulled in, the stopper member 136 of the stopper shaft 131 comes into abutment with the stopper hole 132a in the metal plate 130 as shown in FIG. 7, thus hindering the trigger from being pulled in.
When the trigger is pulled in, the stopper button 143 is pushed. This pushes the stopper member 136 of the stopper shaft 131 outwardly as shown in FIG. 8. Consequently, the stopper member is disengaged from the stopper hole 132a. The trigger is pulled in along the guide slot 133a according to the degree to which the trigger is drawn in. When the trigger is pulled in by a given amount the switch mounted in the switch body is inverted and turned on (see JP-A-2003-109451).
However, the stopper member of one conventional trigger already described is so constructed that the stopper member of the stopper shaft is abutted against the guide slot formed in one wall surface to stop the trigger from being pulled in and, therefore, if the trigger is forcibly pulled in, the trigger and the stopper shaft itself become oblique. As a result, there arises the problem that the stopper member is forced into the guide slot, destroying it.
Furthermore, in the other conventional structure already described, a stopper hole is formed in a metal plate instead of the guide slot formed in one wall surface. Even in this structure, it is impossible to avoid the phenomenon that the trigger becomes oblique as it is pulled in. The pull-in operation is unstable. In addition, an additional metal plate is mounted. Hence, there is the problem that the additional metal plate complicates the structure and increases the number of components.